Evaporator burner for a mobile heating device

ABSTRACT

An evaporator burner for a mobile heating device is provided, with: a combustion chamber surrounding a combustion space for converting fuel with combustion air; an evaporator receiving portion for receiving an evaporator body for evaporating liquid fuel, the evaporator receiving portion being arranged at a rear side of the combustion space; a burner cap which closes the combustion space at the rear side of the evaporator receiving portion and which is connected to the combustion chamber; and a fuel pipe for supplying fuel to the evaporator body, the fuel pipe opening into the evaporator receiving portion. The fuel pipe is thermally coupled to the burner cap and the burner cap is provided with an air heat exchanger for cooling the burner cap over which supplied combustion air is guidable during operation.

The present invention relates to an evaporator burner for a mobile heating device.

Mobile heating devices are known which can e.g. be used as vehicle heating devices for heating a vehicle. In vehicle applications, such mobile heating devices are e.g. employed as supplementary heaters capable of providing additional heat when the propulsion engine of the vehicle is running or as parking heaters capable of providing heat for heating purposes both when the propulsion engine is running and when the propulsion engine is turned off.

In the present context, the term “mobile heating device” means a heating device which is designed and correspondingly adapted for use in mobile applications. This means in particular that it is transportable (e.g. fixedly mounted in a vehicle or only placed there for transport) and not exclusively adapted for permanent stationary use, as would be the case for heating of a building. The mobile heating device can be fixedly installed in a vehicle (land vehicle, boat, etc.), in particular in a land vehicle. In particular, it can be adapted for heating a vehicle interior, such as of a land vehicle, a water vehicle or an air plane, and a partly open room as can be found in boats, in particular yachts. The mobile heating device can also temporarily be used stationary, such as e.g. in big tents, containers (e.g. containers for building sites), and the like. According to a preferred further development, the mobile heating device is adapted as a parking heater or a supplementary heater for a land vehicle, such as e.g. a mobile home, a recreational vehicle, a bus, a passenger car, etc.

In mobile heating devices comprising an evaporator burner, often liquid fuel which can e.g. be the fuel also used for a combustion engine of the vehicle, such as benzine, diesel or ethanol, is fed via a fuel pipe to an evaporator body consisting of a porous, absorbent material. The fuel is evaporated on the evaporator body. The fuel is intermixed with combustion air which is also supplied and converted in an exothermal reaction thereby generating heat. Usually, the evaporator burners are not operated continuously but instead—depending on the required heating power—are relatively often switched on and off again. During turning off, usually first the fuel supply is terminated by switching off a fuel conveying pump and combustion air is at first still supplied in order to enable as much as possible residue-free and clean burning out. As a consequence of this, during the time of burning out when a high temperature still exists in the combustion chamber of the burner, a stationary amount of fuel is present in the fuel pipe. If a relatively good thermal connection exists between the combustion space and the fuel pipe, a high thermal load can act on a stationary amount of fuel in the fuel pipe in particular in the time period immediately after stopping the fuel supply. As a consequence of this, e.g. polymerization of fuel components can take place in the fuel pipe which can result in deposits in the fuel pipe which are not soluble in the unaltered fuel. These deposits can lead to an increase in flow resistance in the fuel pipe and ultimately to plugging of the fuel supply.

It is the object of the present invention to provide an improved evaporator burner for a mobile heating device with which in particular the risk of plugging in the fuel pipe is reduced.

The object is solved by an evaporator burner for a mobile heating device according to claim 1. Further developments are specified in the dependent claims.

The evaporator burner comprises: a combustion chamber surrounding a combustion space for converting fuel with combustion air; an evaporator receiving portion for receiving an evaporator body for evaporating liquid fuel, the evaporator receiving portion being arranged at a rear side of the combustion space; a burner cap which closes the combustion space at the rear side of the evaporator receiving portion and which is connected to the combustion chamber; and a fuel pipe for supplying fuel to the evaporator body, the fuel pipe opening into the evaporator receiving portion. The fuel pipe is thermally coupled to the burner cap and the burner cap is provided with an air heat exchanger for cooling the burner cap over which supplied combustion air is guidable during operation.

By the thermal coupling of the fuel pipe to the burner cap, efficient heat removal from the fuel pipe to the burner cap can take place, thus the fuel pipe can be cooled. At the same time, the burner cap can efficiently be maintained on a relatively low temperature level by heat transfer to supplied combustion air via the air heat exchanger. Since the burner cap is used as a heat sink for the fuel pipe, an additional heat sink for the fuel pipe formed as a separate component can be dispensed with. This allows a cost-efficient and compact realization. Since an undesirably high temperature rise in the region of the fuel pipe can be prevented, the risk of plugging in the fuel pipe is reduced. The air heat exchanger can e.g. be formed as a separate element or can also be formed in one piece with the burner cap from the material of the burner cap.

According to one development, the burner cap is connected to the combustion chamber only via one substantially line-shaped junction. In this case, the heat conduction from the combustion chamber to the burner cap is suppressed since the line-shaped junction allows for at most weak heat conduction towards the burner cap. Thus, the burner cap can reliably be held on a relatively low temperature level and forms a reliable heat sink for the fuel pipe. It is however also possible to realize the burner cap thermally insulated from the burner chamber and other hot components in another manner.

According to one development, the air heat exchanger comprises a plurality of heat exchanger fins. In this case, good heat transfer to the supplied combustion air is achieved by a large surface such that heat can efficiently be removed from the burner cap. The heat exchanger fins can comprise different shapes.

According to one development, the air heat exchanger is arranged in the combustion air supply upstream of the combustion space. The air heat exchanger can in particular be arranged directly upstream of the combustion space to achieve a particularly compact construction. By the arrangement upstream of the combustion space, the combustion air can be pre-heated through this heat transfer before entry into the combustion space.

According to one development, the burner cap is made from aluminum or from an aluminum alloy. In comparison to a realization in which the burner cap is e.g. formed from stainless steel, due to the high heat conductivity of aluminum or aluminum alloys efficient heat distribution and heat removal is provided for in the burner cap in this realization such that the heat to be removed is efficiently removed to the air heat exchanger.

According to one development, the burner cap and the evaporator receiving portion are formed as separate components. In this case, also undesired high heat transfer from the evaporator receiving portion into the burner cap can be prevented such that the burner cap can be maintained on a low temperature as a heat sink. If the burner cap and the evaporator receiving portion are arranged spatially spaced from each other, undesired heat input from the evaporator receiving portion into the burner cap can be prevented in a particularly reliable manner.

According to one development, the combustion chamber comprises a plurality of holes for supply of combustion air into the combustion space.

Further advantages and developments will become apparent from the following description of an embodiment with reference to the FIGURE.

FIG. 1 is a schematic illustration of an evaporator burner for a mobile heating device in the region of an evaporator receiving portion and of a burner cap.

In the following, an embodiment is described with reference to FIG. 1. In FIG. 1, a region of an evaporator receiving portion 2 and of a burner cap 8 of an evaporator burner 1 for a mobile heating device is schematically depicted. In the illustration of FIG. 1, a schematic sectional illustration in a plane containing a main axis Z of the evaporator burner 1 is shown. The evaporator burner 1 can e.g. comprise substantially rotational symmetry with respect to the main axis Z. The evaporator burner 1 can e.g. be formed for a vehicle heating device, in particular a supplemental heater or a parking heater. The evaporator burner 1 is in particular formed to convert a mixture of evaporated fuel and combustion air in a combustion space 4 thereby generating heat. The generated heat is transferred to a medium to be heated in a heat exchanger (not shown). The medium to be heated can e.g. be formed by air or by a cooling liquid. In the schematic illustration of FIG. 1, in particular the heat exchanger, the discharge line for the hot combustion exhaust gases, the combustion air conveying device (e.g. a blower) which is also provided, the fuel conveying device (e.g. a metering pump), the control unit for controlling the evaporator burner 1, etc. are not depicted. These components are well known and described in detail in the prior art.

The evaporator burner 1 comprises an evaporator receiving portion 2 in which a porous, absorbent evaporator body 5 is arranged. In the embodiment, the evaporator receiving portion 2 comprises a substantially cup-shaped shape with a hole in the bottom. The evaporator body 5 is accommodated in the cup-shaped depression of the evaporator receiving portion 2 and can in particular be fixedly held therein, e.g. by welding, soldering, clamping or making use of a suitable securing element. The evaporator body 5 can e.g. in particular be formed by a non-woven fabric of metal fibers or by a plurality of layers of non-woven fabric of metal fibers.

A fuel pipe 6 for supplying fuel to the evaporator body 5 is provided. The fuel pipe 6 opens into the evaporator receiving portion 2 and is connected to a fuel conveying device (not shown) by which fuel can be conveyed through the fuel pipe 6 in a predetermined amount, as schematically depicted by an arrow B. The fuel pipe 6 is fixedly connected to the evaporator receiving portion 2, e.g. by welding or soldering.

The combustion space 4 is circumferentially bordered by a combustion chamber 7 which can e.g. be formed by a substantially cylindrical component made of temperature resistant steel. The combustion chamber 7 is provided with a plurality of holes 7 a via which the combustion air can be supplied to the combustion space 4, as schematically illustrated by branching arrows in FIG. 1.

Further, a burner cap 8 is provided which closes the combustion space 4 at the rear side of the evaporator receiving portion 2. The burner cap 8 is made from aluminum or from an aluminum alloy and can e.g. be produced in a die casting process. The burner cap 8 also comprises a substantially cup-like shape and is arranged such that a surrounding side wall reaches around the evaporator receiving portion 2. The burner cap 8 and the evaporator receiving portion 2 are formed as separate components which are arranged spatially spaced from each other. In a bottom region of the burner cap 8, a through-hole is provided through which the fuel pipe 6 passes. The combustion chamber 7 is fixedly connected to the burner cap 8 such that the combustion space 4 is closed at the rear side. In the embodiment, the combustion chamber 7 is connected to the burner cap 8 only via a substantially line-shaped junction. In the embodiment, the circumferential side wall of the burner cap 8 comprises a circumferential narrow protruding rib 8 a to which the combustion chamber 7 is fixed in a substantially line-shaped way. The combustion chamber 7 can be fixed to the protruding rib 8 a by e.g. welding, soldering or caulking. Due to the connection of the combustion chamber 7 to the burner cap 8 only via the protruding rib 8 a, heat transfer from the combustion chamber 7 to the burner cap 8 via heat conduction is suppressed or strongly reduced, respectively, so that the protruding rib 8 a serves as thermal insulation for the burner cap 8.

The fuel pipe 6 is thermally coupled to the burner cap 8 such that heat transfer from the fuel pipe 6 to the burner cap 8 can take place. In the depicted embodiment, the fuel pipe 6 comprises a circumferential projection 6 a via which the fuel pipe 6 is heat-conductively connected to the burner cap 8. The connection can e.g. be realized by soldering or welding. Instead of a circumferential projection 6 a, the heat pipe 6 can also be heat-conductively connected to the burner cap 8 in another manner. For example, a heat-conductive element, such as a heat-conductive pad, can also be provided between the fuel pipe 6 and the burner cap 8 for heat exchange.

The burner cap 8 is provided with an air heat exchanger 8 b for cooling or heat removal, respectively, from the burner cap 8. The air heat exchanger 8 b comprises a plurality of heat exchanger fins (preferably a multitude of heat exchanger fins) which are distributed over the outer circumference of the burner cap 8. The heat exchanger fins project into the flow of combustion air in a combustion air supply upstream of the combustion space 4. In operation, the supplied combustion air flows around the heat exchanger fins, as schematically depicted by arrows L in FIG. 1, such that combustion air is fed over the air heat exchanger 8 b and that the burner cap 8 is cooled in this way. The air heat exchanger 8 b can e.g. be formed in one piece with the burner cap 8 from the material of the burner cap 8 or can also be heat-conductively coupled to the burner cap 8 as a separate component. E.g. the air heat exchanger 8 b can be formed by heat exchanger fins molded on the outer wall of the burner cap 8.

Due to the described realization, in the embodiment the fuel pipe 6 is thermally coupled to the burner cap 8 such that the burner cap 8 serves as a heat sink for the fuel pipe 6. Due to the construction out of aluminum or an aluminum alloy, the burner cap 8 comprises high heat conductivity and the heat is efficiently conducted to the air heat exchanger 8 b at which it is transferred to the supplied combustion air. Further, in this way the temperature of the burner cap 8 is maintained as low as possible during operation such that thermal insulation of the burner cap 8 from hot components is provided. This is e.g. achieved in that the combustion chamber 7 is connected to the burner cap 8 only through a substantially line-shaped junction and not through a plane-shaped contact area.

Since the burner cap 8 efficiently serves as a heat sink for the fuel pipe 6 in the described manner, conglutination or plugging of fuel in the fuel pipe 6 due to an undesired large heat input can reliably be prevented without requiring a separate heat sink as a separate additional component.

Although this is not illustrated in FIG. 1 and was not explicitly described, the combustion space 4 is surrounded in known manner by a heat exchanger for transferring the heat which is set free to a medium to be heated, such as air or a fluid. Further, a casing is provided in a manner per se known in which the evaporator burner is accommodated and which provides appropriate air conductance for the combustion air supply. 

1. An evaporator burner for a mobile heating device, comprising: a combustion chamber surrounding a combustion space for converting fuel with combustion air; an evaporator receiving portion for receiving an evaporator body for evaporating liquid fuel, the evaporator receiving portion being arranged at a rear side of the combustion space; a burner cap which closes the combustion space at the rear side of the evaporator receiving portion and which is connected to the combustion chamber; and a fuel pipe for supplying fuel to the evaporator body, the fuel pipe opening into the evaporator receiving portion; wherein the fuel pipe is thermally coupled to the burner cap and the burner cap is provided with an air heat exchanger for cooling the burner cap over which supplied combustion air is guidable during operation.
 2. The evaporator burner according to claim 1, wherein the burner cap is connected to the combustion chamber only via one substantially line-shaped junction.
 3. The evaporator burner according to claim 1, wherein the air heat exchanger comprises a plurality of heat exchanger fins.
 4. The evaporator burner according to claim 1, wherein the air heat exchanger is arranged in the combustion air supply upstream of the combustion space.
 5. The evaporator burner according to claim 1, wherein the burner cap is made from aluminum or from an aluminum alloy.
 6. The evaporator burner according to claim 1, wherein the burner cap and the evaporator receiving portion are formed as separate components.
 7. The evaporator burner according to claim 6, wherein the burner cap and the evaporator receiving portion are arranged spatially spaced from each other.
 8. The evaporator burner according to claim 1, wherein the combustion chamber comprises a plurality of holes for supply of combustion air into the combustion space. 